An analysis of crude oil–acid reaction products by size-exclusion chromatography

The contact of acid with crude oil generates a reaction product known as acid-sludge which has been interpreted as polymerised asphaltenes due to Friedel–Crafts reactions. A size-exclusion chromatographic analysis of crude oils and fractions showed, however, that acid-sludge is composed of small molecules. The greatest increase in molecular weight was observed for the nonpolar fractions. The results could be explained by assuming surfactant-like behaviour of protonated basic crude oil components. Aggregate formation, therefore, explains the higher molecular weights observed.